This invention relates generally to the fusion of polypropylene piping system components and more particularly concerns a tool and method for fusing outlet fittings in a plastic pipe.
The fusion of outlet fittings is an alternative to the prior practice of removing a section of pipe from a piping system and welding a pipe-tee between the cut ends. Pipe-tees are often added to piping systems already installed in horizontal, vertical and other angular orientations in ceilings, walls and other confined areas which impose awkward restraints on the operator adding the pipe-tee.
A common first phase of the fusion process is to drill a hole for the fusion outlet fitting in the receiving pipe. Precise radial alignment of the hole is critical to achieving proper fusion of the fitting to the pipe. That is, the center axis of the finished hole should be perpendicular to a tangent to the wall of the pipe and intersect the longitudinal center axis of the pipe. Unfortunately, this seemingly simple precondition poses significant compliance problems. For one, since the hole must be drilled into the cylindrical outer wall of the pipe, the drill bit tends to “walk” the pipe surface as boring begins. As the bit “walks,” the intended point and angle of entry of the bit into the pipe changes. For another, the pipe may be loosely secured to the structure or may be secured by structure, such as relatively long or flexible hangers or threaded rods, which is unable to maintain pipe stability during the drilling phase of the process.
The hole drilling phase is followed by the heating phase of the fusion process. The hole is deburred and cleaned out, a constant heater temperature level is established, the heater is inserted into the hole at a force sufficient to create a consistent melt pattern on the diameter of the pipe, the fitting is attached to the heater and any misalignment is corrected by rolling the heater around in the hole or rocking the fitting from side to side in order to get the entire perimeter to show an apparent sign of melt. The rolling and rocking of the heater and fitting bring into play the risks of inconsistent heating of parts of the fitting or pipe and, ultimately, a suboptimal finished joint. The heater is removed from the pipe and fitting when the presence of melted plastic around the entirety of the fitting and pipe are observed.
Inserting the fitting into the pipe happens quickly and often requires a considerable amount of force. As the fitting is pressed into the hole, the pieces of melted plastic begin to combine into one solid piece. There is presently no accurate way to determine whether a fitting is aligning concentrically in a hole. There is presently no machine available as an aid in the entire process of fusing an outlet fitting to a polypropylene piping system. Therefore, fittings are anticipated to be the most likely failure points within a piping system.
Some drilling machines are available with a guide way system translating a drill motor towards and away from metallic or plastic pipes. A few saddle style fusion machines for polyethylene piping systems have the ability to fuse an outlet joint but do not drill a pilot hole, as this style of fitting does not require the hole to be pre-drilled.
It is, therefore, an object of this invention to provide a tool for and method of consistently producing satisfactory outlet fitting fusions. Another object of this invention is to provide an outlet fitting fusion tool which is connected directly to the pipe. It is also an object of this invention to provide an outlet fitting fusion tool capable of establishing a rigid structure and a point of reference for the entirety of the fusion process. And it is an object of this invention to provide an outlet fitting fusion tool capable of maintaining concentricity of a fusion joint throughout the drilling, heating, and fusion phases of the outlet fitting fusion process.